Media insertion systems involve the selection of a media item for output by a receiver during a predefined slot in a schedule either at time of broadcast or when playing back recorded or video-on-demand (VOD) programming, such as from a Personal Video Recorder (PVR). Where the programming includes content during the slot which may be replaced by media insertion, this replacement in referred to as media substitution. Such systems may be used for targeted substitutional advertising (TSA), where an advertisement (a commercial in US English) is selected for output based on a predefined user profile, without specific selection of the advertisement by the user. In a broadcast example, the user experience is similar to watching a broadcast with an advertising break, but the advertisements are tailored to the user profile by means of a selection made at the broadcast receiver. A default media item may be included in the broadcast programming during the slot, for output by receivers in which media substitution is not enabled, or by receivers not targeted by the substitution.
Attempts have been made to standardise aspects of media insertion. For example, the Society of Cable Telecommunications Engineers standard SCTE 130-1 2008 defines a framework of XML interface standards for communication between different components of a substitutional advertising platform. The Advanced Advertising 1.0 specification was announced by Canoe Ventures LLC on 30 Mar. 2009.
However, the practical implementation of a media substitution or insertion system raises many challenges. One problem is the complexity of scheduling media items that are subject to constraints, for example relating to other media items to be scheduled or to scheduled programmes, particularly when output proximate or adjacent to each other. Constraints in current linear (i.e. non-substitutional) advertisement scheduling systems already involve a considerable level of complexity. For example, the applicant's Landmark 2 system requires a dedicated state of the art computer system to perform the constraint satisfaction necessary to manage advertisement scheduling in over 200 channels. Performing substitutional booking within the same system context as linear booking would involve an unmanageable level of complexity if constraints were to be satisfied between all possible substitutional options. One specific problem is the limited processing power available at the receiver to select substitutional options.
In a centralised broadcast system, such as a satellite broadcast system, regional variations in the media items must be handled by means of substitution or insertion, rather than by transmitting regional variations only from the corresponding regional headends.
Another problem with media substitution involves determination of which media items have been output at the receiver. Currently, such information is obtained from survey data from a relatively small number of users, although more accurate information could be provided over a return link. However, the receiver may not have a return link available, or it may be desirable to avoid using the return link, for example where the return channel is over a dial-up modem connectable to the user's main telephone line. Users may also be averse to systems which report specific user behaviour to a remote site.
Another problem involves the method of selecting the substitutional media items to be output by the receiver, according to the user profile. It would be desirable for the selection criteria to be as flexible as possible, but this would involve storing a large quantity of profile data at the receiver. Furthermore, the broadcast receiver may not be capable of applying complex selection rules to determine which media item to output.
Another problem involves controlling the probability that a particular media item or set of media items will be output by a particular receiver. In linear scheduling systems, predicted audience figures and profiles for a particular programme are used to select which advertisements should be scheduled in a break within or adjacent that programme. The predicted audience figures are provided in the UK by the Broadcasters' Audience Research Board (BARB). The probability of a particular advertisement being output by a particular receiver is simply determined by the probability of that receiver being tuned to the channel in which the advertisement is scheduled, during the time slot in which the advertisement is scheduled. That probability is a function of the audience segment to which the receiver belongs.
In a media substitution system, the probability of a particular substitutional advertisement being output by a particular receiver is also dependent on the probability of that substitutional advertisement being selected by the receiver. Although predicted audience figures may be broken down by audience segment, these segments may not correspond to the segments at which the different substitutional options are targeted. Therefore, predicted audience figures are less useful for scheduling substitutional media items than for scheduling linear media items.
It would therefore be desirable to control the delivery of substitutional media items so as to optimize the probability of a particular media item, addressed to a selected audience segment, being output by receivers falling within that audience segment.
Another problem arising from substitutional media insertion is the need to make the transition in an output stream between a broadcast or playback programme and a substitutional item as seamless as possible. Ideally, the transition should be imperceptible to the user, so that the user experience is indistinguishable from watching a media item, such as an advertisement, included as part of a broadcast or playback programme. However, the use of digitally encoded video and audio data presents particular problems in splicing a substitutional media item into an output stream.
Digital video broadcasts typically comply with the DVB standards, such as DVB-T for terrestrial and DVB-S for satellite, which specify the use of interframe video compression such as MPEG-2. Therefore, at least some of the video frames are encoded with reference to a preceding frame (P frames) or with reference to preceding and following frames (B frames). Splicing one video stream into another video stream may disrupt the encoding scheme, for example if a B frame of one stream is followed by a P or B frame of the other stream, such that severe decoding errors occur.
At least some of the video frames may have an associated time reference, such as the presentation time stamp (PTS) included in MPEG-2 video streams, to assist with audio synchronisation. The time reference of a broadcast stream may indicate the time of broadcast. However, a substitutional media item will typically have a completely different time reference from the broadcast or playback stream. When a substitutional media item is spliced into a broadcast stream, the resultant discontinuity in time references may cause problems in the audio and video decoders, such as loss of audio synchronisation or audio muting.
Audio decoding of substitutional content presents a particular problem, since audio decoding may be performed by an external decoder that is not aware of when splicing has occurred, and is not designed to handle spliced audio content. Any apparent errors in the audio stream caused by splicing will lead to unpredictable results at the audio decoder.
Another problem may incur in the indication of splice points to a broadcast encoder. The system upstream of the encoder indicates the splice points using a time reference, while the encoder encodes the splice point with reference to a specific video frame. Since the indicated time may not correspond precisely to the start of an encoded frame, there is an uncertainty of up to one frame period in the encoded position of the splice point.
The above problems are not confined to broadcast systems, since video on demand (VOD) and push video on demand systems (PVOD) may include substitutional content with a requested programme; see for example the applicant's patent publication WO 2008/078093 A1, concerning the linking of secondary assets, such as advertisements, with a primary asset, such as a requested programme.